1. Field of the Invention
This invention relates to the testing of cigarettes and similar rod-like articles, having an air-pervious filling and an open-ended wrapping for the filling, for leaks in the wrapping.
2. Description of the Prior Art
In the case of cigarettes, such leaks can render them impossible or very unsatisfying to smoke. For very many years, it has been the practice in the cigarette-manufacturing industry for each of the cigarettes coming off a cigarette-making machine to be inspected by an operator. With modern speeds of production of cigarettes, which are at the rate of several thousand per minute, it becomes desirable to replace this manual inspection with an automatic testing apparatus which will receive a continuous high speed stream of cigarettes from a cigarette maker, test them, reject those that are unsatisfactory and pass the good ones on to be conveyed to packing machinery. In recent times, various proposals for the construction of such apparatus have been made.
In U.S. Pat. No. 3,608,380, there is disclosed a construction of apparatus in which a pressure difference is established across the cigarette wrapping by applying suction outside the cigarette, the pressure within the cigarettes being measured to indicate any leaks. This is done by forming an individual testing chamber around each cigarette and applying suction to that chamber. When the measured pressure at the end of the cigarette, relative to atomospheric pressure, exceeds a preset level a reject signal is generated, whereby the faulty cigarette is suitably rejected. In particular, a jet air producing means including a tube and an actuatable valve is disposed adjacent a reject point on a separate fluted drum downstream of the test point, whereby the faulty cigarette is suitably rejected. In particular, a jet air producing means including a tube and an actuatable valve is disposed adjacent a reject point on a separate fluted drum downstream of the test point, whereby the faulty cigarette, when it is moved to the reject point, is rejected by opening the valve to permit the air jet to discharge the cigarette from the drum. However, no means is described in the above-noted U.S. Pat. No. 3,608,380 for accurately and conveniently calibrating the inspection device so that it will reject cigarettes with defects in the cigarette wrapper greater than an acceptable size.
In actual use of cigarette inspection devices or apparatus as described in the above identified U.S. patent, there have been developed several methods whereby such testing apparatus may be empirically, but somewhat inaccurately calibrated. First, the test operator may conduct an efficiency test drilling a hole, typically in the order of 1/16 inch in a bobbin of cigarette paper, before it is wrapped about the tobacco core, and subsequently making cigarettes with this bobbin of paper. While such cigarettes are being tested, the sensitivity control of the inspection device is varied until a certain percentage of the cigarettes made with the 1/16 inch diameter hole are rejected. In the alternative, the test operator may vary the sensitivity control until a certain number of good cigarettes are rejected over a unit time interval, which, from experience with other cigarette inspection apparatus, would be the proper setting. However, there is no known prior means for setting the calibration of such test apparatus with respect to known defects within the cigarette such that the cigarette inspection device will not reject cigarettes that are otherwise acceptable or that the critical level has been set precisely between known defect limits that are readily ascertained to be unacceptable and acceptable.
the inability to accurately and conveniently calibrate such cigarette inspection apparatus leads to the rejection of cigarettes that would otherwise be acceptable. For example, when the manufacturing operation is interrupted upon exhaustion of the supply of the paper wrapping, a new bobbin of cigarette paper wrapping is installed and thereafter the cigarette manufacturing is recommenced. However, the porosity of cigaratte wrapping paper does vary from bobbin to bobbin, and unless the sensitivity of the test circuit is readjusted for the new wrapping paper, cigarettes may be rejected that otherwise would be acceptable, or cigarettes with defects that normally would be rejected may be deemed acceptable by the test apparatus.